I've used built in SD card modules in the past (using things like the Quartus system builder thingy). Sounds like you're on the right path, I like that you have an intermediate step here to get it decoupled from the desktop. Keep it up!

Thanks Chris for the encouragement. Your comment about having intermediate steps reminds me of the movie What About Bob. I'm not sure if you've seen the movie, but in it a psychiatrist Dr. Leo Marvin (Richard Dreyfuss) tries to help a new patient Bob Wiley (Bill Murray), who suffers from a host of phobias. Dr. Marvin prescibes his newly released book entitled "Baby Steps" to Bob in hopes that it'll help him with his problems. Of course, as the name suggests, the book aims to help patients find relief from their troubles by giving them a series of small bite sized goals (baby steps) on their road to recovery. I have found the same approach to be helpful with both software and now hardware design. The end goal is to have a finished thing that works, but getting to that goal you can have a series of smaller goals that you can accomplish along the way. So for example with this current NES project, the small goals might include 1.) getting VGA to work 2.) adding the TFT LCD 3.) adding the controller 4.) adding the menu ...etc. Anyway, all that to say, it's a great movie if you haven't seen it.

After recovering from turkey coma's and holiday festivities, I managed to do a bit of soldering recently. I had the need for a LIR2032 coin cell charger to power a few projects. Unfortunately (or fortunately depending on how you look at it) , the charger I had ordered off Amazon didn't work, so I decided to build my own. I took the guts of the Solder Sniffer 9000 project, which consisted of a MCP73831 for the charge controller, and modified it a bit to charge an LIR2032.

The main change needed was the value of R3, which is responsible for setting the max charge current. For the LIR2032, the max charge current is 35mA. By using the supplied formula in the MCP73831 datasheet (I = 1000V/R) I was able to find that a 28K resistor would give me the charge current needed.

To get a decent connection to the USB socket, I tinned each of the pads a bit.

I had the opportunity to solder up another board recently. I've been wanting to play around with OLED displays for a bit, and was looking to buy a breakout board. I found this 1.5" 128x128 color OLED board on Adafruit that looked promising, however it didn't provide access to the parallel interface pins of the SSD1351 driver. In order to drive the display at a high frame rate I wanted to connect to the parallel interface of the OLED, so I decided to make my own board.

I started searching around to see if I could find another similarly sized OLED display with the SSD1351 driver. I ended up finding this one from buydisplay.com. Looking at the datasheet, it seemed basically identical to the OLED on Adafruit, so I decided to buy one to test it out.

I used the schematics of the Adafruit board as a jumping off point, but made a few changes. I took out the SD card holder, since I didn't really need that functionality. I took out the 3.3v regulator and level shifter, since I wanted to power the board directly with 3.3v. I broke out all of the control pins to a header where they could easily be plugged into a breadboard for prototyping. I left in the FAN5331SX boost converter which boosts the 3.3v to the 13v that the OLED requires.

I'm glad I looked through your old posts because I was looking to build a fume extractor and it looks like your Solder Sniffer would be a great little project. I also wanted something that would run on a spare 18650 that I have laying around. Thanks for adding all the info on GitHub and may post questions in the future when I get around to ordering the parts. I believe I also have a spare 120mm fan so will probably just use a prototype board or create a new PCB.

Thanks @BlakeL! The Solder Sniffer is by far my most used project. If you were thinking of ordering boards to build one, I can just send you one of my extra boards since my original shipment came with 10. Just a fair bit of warning - depending on your comfort level with soldering SMD components, there may be one or two components that are a bit challenging, like the SOT23 and MicroUSB. I wasn't sure there would be that much interest in this project, but now that I know there is, I may revise it a bit to make it a little easier to solder. I know for starters I could extend the pads out a bit on the components to get a little more wiggle room for the iron.

Thanks, that would be very helpful. I can message you my address. The board can probably be adapted to a 120mm fan or if I put it inside a wooden enclosure, I could mount the board inside. The SMD parts I know will be difficult but I've watched quite a few videos and all I think I need is to buy some flux.

I cleared off enough room on the workbench to do some more testing on my spartan mini fpga board with the end goal of completing this handheld NES project. Of course to be truly portable, I didn't want to have to reprogram the NES core into the FPGA each time I wanted to play a game. It would be nice to persist the FPGA configuration off to the external SPI flash attached to the Spartan 6, and have it load in that configuration automatically when it starts up.

Here's the pertinent part of the spartan mini schematic, showing the connections to the SPI flash:

The spartan 6 provides a way to read configuration data from an attached SPI flash. The Xilinx Impact software is used to program the SPI flash via an indirect programming method. This all seemed pretty simple and straightforward, at least on paper. But my friend Murphy likes to show up and tell me that I can mess up even the simplest of things.

After squandering what seemed like countless hours of my life, messing around with the Impact software, I was getting nowhere. I was getting the error message "spi device not found, id check failed". That's odd I thought, I see it right there in front of me, why can't it find it? I ignored everything Chris had taught about whipping out the logic analyzer and checking the signals on the board. My every failed instinct seemed to take me further down the rabbit hole. I went to the schematic to see if maybe I had set the wrong mode configuration on the fpga. Then I went to check the schematic for the flash, to make sure it looked ok. I looked for clues from the manufacturer datasheet on what I was doing wrong.

Finally, when I had exhausted every last possible resource I could think of, I fished out the logic analyzer from the garage storage and clamped some probes onto the circuit :). I hooked up the probes to the chip select, data, and clock lines. To my astonishment, not a whole lot was going on. The clock was cycling a few times, but no other communication was really happening. This prompted me to start probing with the multi meter. The voice of Dave Jones echoed in my head "Thou shalt check voltages". After confirming the voltages looked ok, I started checking for continuity between the various spi pins to the fpga. It was at this step that I found that there was no continuity between the chip select pin on the flash and the fpga. Aha! Finally I was getting somewhere. Looking at the schematic I saw that there was a 0 ohm resistor(R18) in series with the chip select pin, so I checked for continuity to it, but got nothing. Thinking it may be just a bad solder joint, I was about to grab the iron to re-flow the solder, when the multi meter probe glanced off of R20, a 10k pull-up resistor, and to my surprise I got a chirp indicating that there was continuity between that and the chip select. I pulled up the board file for these 2 resistors to see what was happening.

When I selected R18 in pcbnew, the problem became obvious. The R18 and R20 reference designators were swapped. So instead of soldering in a 0 ohm resistor on R18, I had seen the misplaced reference and placed a 10K resistor in its place. Mystery solved! After switching the resistor values, I fired Impact up, and was able to save the configuration off to the spi flash without a hitch. I guess there's a few lessons I want to take away from this whole experience. First, make sure to pay extra attention when placing those references, that they're next to the right component. And second, don't wait so long to reach for the trusty logic analyzer or oscilloscope when problems arise. This may be one of the classic "trap for young players" that Dave mentions on occasion.

Spent some more time soldering the final handheld NES project. Just like in routing PCB traces, the majority of the time seems to be in getting the placement of the components just right. For this particular project it wasn't too bad. My main concern was just aligning the components so that they wouldn't hinder the connection between the FPGA board and the proto shield. I wired in a Parallax Propeller Mini board to save on space. Here's what the finished placement looks like:

I cut a small slot for the lcd cable to enter through the board and connect to the led driver. I ended up desoldering the screw terminals from the audio amp board in order to save room for the usb plug.

I finished up the Spartan Mini NES project today. This is a project developed around my Spartan 6 FPGA development project. The end goal of this project was to learn Verilog and FPGA design, while also creating a handheld NES gamepad. I left off last time with the wiring done to the perfboard shield that connects to the FPGA board. Since there wasn't enough room on that board to place the display and all the buttons I decided to bolt the shield to a larger perfboard that would fit all the components needed. I ran some measurements on the largest perfboard I had and mounted the shield to the board.

For the power supply I used 4 AA batteries wired in series and plugged directly into the barrel jack on the Spartan Mini board. I found that by placing the battery packs on the outer edge of the board, they could double as handle grips. I used velcro to hold down both the display as well as the battery holders. I did this in the hopes that it would be easier to modify or repair the board if it was needed in the future.

I'm going to swap out the Alkaline batteries for some NiMH 2100mAh rechargeable batteries. The total current drain of this project as measured by my power supply was around 400mA, so hopefully that should give me around 5 hours or so of operation before recharge. All in all I'm happy with how this project turned out. It was a lot of fun diving into FPGA's and being challenged by aspects of electronics that I hadn't encountered before.